Flame retardant

ABSTRACT

Flame retardant protection has been demonstrated on cotton and on polyester-cotton materials by the product obtained from the reaction of cyanamide and PCl 5  followed by reaction with anhydrous ammonia in excess of that required to react with the chlorine on the cyanamide and PCl 5  intermediate product. Conveniently the material can be treated with an aqueous solution containing a sufficient amount of the new flame retardant compound and the material dried to make the material self extinguishing. Then the treated and dried material is cured at a sufficient temperature to bond the flame retardant to the material. Alternatively and usually preferably, the drying and curing can be accomplished as a single operation.

This is a division of application Ser. No. 490,608, filed July 22, 1974,now U.S. Pat. No. 4,000,191.

BACKGROUND OF THE INVENTION

1. Field of the invention

Fireproofing.

2. Description of the prior art

One of the older patents in this art is U.S. Pat. No. 2,782,133 teachingaminocyclophosphazene as a fireproofing agent for cellulosic fibers suchas cotton. A recent patent is U.S. Pat. No. 3,711,542 teaching certainnew N-methylol phosphazene compounds as flame retardants on cotton, andthis patent under Background of the Invention contains a summary ofcertain phosphazene prior art on flameproofing.

SUMMARY OF THE INVENTION

Flame retardant protection has been demonstrated on cotton and onpolyester-cotton materials by the product obtained from the reaction ofcyanamide and PCl₅ followed by reaction with anhydrous ammonia in excessof that required to react with the chlorine on the cyanamide and PCl₅intermediate product. Conveniently the material can be treated with anaqueous solution containing a sufficient amount of the new flameretardant compound and the material dried to make the material selfextinguishing. Then the treated and dried material is cured at asufficient temperature to bond the flame retardant to the material.Alternatively and usually preferably, the drying and curing can beaccomplished as a single operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preparation of product

The structure for the product of the reaction of cyanamide withphosphorus pentachloride, then ammonia is believed to be

    [(NH.sub.2).sub.3 P═N--C.tbd.N].sub.n

based on the following reaction

    H.sub.2 NCN + PCl.sub.5 → N.tbd.C--N═PCl.sub.3 .sup. NH.sbsp.2  N.tbd.C--N═P(NH.sub.2).sub.3 + 3NH.sub.4 Cl

It was hoped that the peraminated compound would be an active monomeranalogous to acrylonitrile. ##STR1## However the infrared spectrum ofthe crude product does not show nitrile absorption but instead indicatessomething akin to carbodiimide absorption. This indicates at least adimeric structure ##STR2## or possibly a linear oligomer. Thetrichloro-precursor and amminated products are both new compositions.

One hundred and twenty-four and a half grams (0.60 m) of PCl₅ were addedrapidly to a slurry of 25.0 g (0.60 m) of cyanamide (EKC, practical) in500 ml of chloroform with stirring. There was immediate reaction withthe evolution of hydrogen chloride gas. After the initial reaction hadsubsided, the mixture was heated to reflux and kept there for 18 hours.The resultant, milky slurry was placed under vacuum to remove dissolvedhydrogen chloride. An additional 500 ml of chloroform was added followedby the cautious addition of 500 ml of liquid ammonia. The ammonia wascontained by a Dry Ice condenser. The excess ammonia was allowed toevaporate overnight.

Evaporation of a sample of the supernatant liquid left no residue. Theslurry was mixed with 131.4 g (1.8 m) of diethylamine and refluxed for 7hours to remove the ammonium chloride as ammonia and chloroform solublediethylamine.sup.. hydrochloride. After standing over the weekend, thewhite solid was filtered from the red solution and washed with 500 ml ofchloroform. The material appeared to be hygroscopic, so it was subjectedto vacuum to remove the remaining chloroform, weight 85.0 g.

The infrared spectrum of this product showed --NH absorption and had amoderately strong band at 2155 cm⁻ ¹ which suggests cyclization to givea carbodiimide structure. There was also strong absorption at 6.4 and8.5μ.

The product, a free-flowing, nonhygroscopic, white powder, wasmoderately soluble in water yielding a weakly alkaline solution. Thematerial was insoluble in hot cyclohexene, xylene, toluene, THF, DMAC,DMF, pyridine, ethyl acetate, methylene chloride, trichloroethylene,ethanol, nitrobenzene and HMPA. The material shrinks at 93° C. in amelting point tube, softens as 120° C. forming a soft foam, expanding upthe tube. The evolution of gas is noted. The crude product had 19.8%phosphorus and contained chlorine. Recrystallization from water raisedthe phosphorus content to 22% (theoretical 26%) and the chlorine wasalmost entirely removed.

    ______________________________________                                         %   Calc'd for CH.sub.6 N.sub.5 P                                                                  Recrystallized Product                                  ______________________________________                                        C    10.10            12.10                                                   H    5.04             4.95                                                    N    58.80            48.80                                                   P    26.10            21.89                                                    Cl  0.00             0.30                                                    ______________________________________                                    

Treatment of fabrics

A solution containing the desired weight percent of the flame retardantreagent in sufficient water to just saturate the cloth was poured on aweighed piece of cloth lying flat in a plastic bag. The solution wasworked over the surface of the cloth, until it was uniformly wet. Afterstanding for about fifteen minutes, the cloth was placed in an oven atthe desired temperature and dried and cured. After drying and curing,the cloth was allowed to equilibrate before being weighed.

Cure conditions

Cure was effected at 140° C. using the one operation to also dry the wetsample. Formaldehyde and magnesium chloride catalyst were included as anauxiliary treatment in some instances in an attempt to make the materialmore durable to washing.

Flammability tests

Samples of cloth 10 in. ×31/2 in. were clamped in a metal stand andtested according to AATC Test Method 34-1969 using a propane torch inplace of the special gas mixture. This flammability test is described inJ. Amer. Assoc. Text. Chem. and Colorists 2, (3), 49/19 (1970).

Tabulation of data

The test data are tabulated in the following table. The table is dividedinto three main sections: Fabric Treatment, Flammability Tests andMiscellaneous Conditions. The following column headings are used. Theadded notes are for explanation of their meanings where not selfexplanatory.

    ______________________________________                                        Column Heading       Explanation                                              ______________________________________                                        1      Cloth Type                                                             2      Reagent       * = Cyanamide/PCl.sub.5 /NH.sub.3 product                3      Auxiliary     material used to bind to cloth                                                such as formaldehyde and                                                      catalyst                                                 4      % Final Add-On                                                                              weight percent of product                                                     added to the cloth after all                                                  processes including                                                           laundering if indicated in                                                    column 9                                                 5      Distance      this represents the length                                      Burned, in.   of the sample that was                                                        burned out, charred or                                                        scorched from the ignited edge                           6      Time,Sec.     time from ignition to removal                                                 of flame even though self                                                     extinguishment had already                                                    occurred                                                 7      SE            answers question -- Did the                                     (Self Extinguish)                                                                           fire self extinguish before                                                   burning the entire sample                                                     length? Y = yes; N = no                                  8      Cure Temperature                                                                            temperature at which the wet                                                  cloth was dried and cured                                                     in a single operation                                    9      Post Treatment                                                                              indicates treatment of sample                                                 after curing but before                                                       flammability test.                                                            L = laundered, detergent wash                                                 and dried; NL = not laundered                            ______________________________________                                    

    __________________________________________________________________________                                           Miscellaneous                          Fabric Treatment           Flammability Test                                                                         Conditions                             __________________________________________________________________________                          %    Distance    Cure                                                         Final                                                                              Burned,                                                                            Time,  Temp.                                                                             Post                               Cloth Type                                                                             Reagent                                                                            Auxiliary                                                                             Add-On                                                                             in.  Sec SE ° C.                                                                       Treatment                          __________________________________________________________________________    65/35                                                                         polyester/cotton                                                                       *    --      20.8 5    30  Y  140 NL                                 65/35                                                                         polyester/cotton                                                                       *    --      12.6 10       N  140 L                                  cotton   *    --      16.8 31/2 30  Y  140 NL                                 cotton   *    --      5.78 3    30  Y  140 L                                  65/35                                                                         polyester/cotton                                                                       *    CH.sub.2 O, MgCl.sub.2                                                                2.8  10   10  N  140 L                                  cotton   *    CH.sub.2 O, MgCl.sub.2                                                                3.4  10   10  N  140 L                                  65/35                                                                         polyester/cotton                                                                       *    --      5.67 10   15  N  140 L                                  50/50                                                                         polyester/cotton                                                                       *    --      10.8 10   20  N  140 L                                  __________________________________________________________________________     *Cyanamide/PCl.sub.5 /NH.sub.3                                                SE = Self Extinguishing                                                       Y = Yes                                                                       NL = Not Laundered                                                            N = No                                                                         L = Laundered                                                                Note: Untreated cotton and cotton/polyester cloths are not self               extinguishing in the flammability test.                                  

Although the invention has been described in terms of specifiedembodiments which are set forth in considerable detail, it should beunderstood that this is by way of illustration only and that theinvention is not necessarily limited thereto, since alternativeembodiments and operating techniques will become apparent to thoseskilled in the art of the disclosure. For example, an auxiliarytreatment of the cloth with formaldehyde plus a quaternary base or anaminoplast such as trimethylolamine with or without a quaternary basemay be useful in making the material more durable to washing withretention of flame retardant properties. Also, other types of celluloseas well as cotton are made flame retardant by the process of theinvention, for example, paper and cellulose sponge. Accordingly,modifications are contemplated which can be made without departing fromthe spirit of the described invention.

What I claim is:
 1. A process for making flame-retardant material ofcellulose such as cotton, paper and sponge or polyester-cotton havingabout 30 to 70% by weight cotton comprising treating said material withan aqueous solution of the product made by reacting cyanamide with PCl₅followed by reaction with anhydrous ammonia in excess of that requiredto react with the chlorine on the cyanamide and PCl₅ intermediateproduct in sufficient amount and curing the treated material at asufficient temperature to make the treated and cured materialself-extinguishing when subjected to a flame-sufficient to ignite andconsume the untreated material.
 2. A process of claim 1 wherein saidmaterial comprises about 65% by weight polyester and 35% by weightcotton.
 3. A process of claim 1 wherein said material comprises about50% by weight polyester and 50% by weight cotton.
 4. A process of claim1 wherein said material comprises cotton.
 5. A flame-retardantpolyester-cotton material made by the process of claim
 1. 6. Aflame-retardant cellulose material made by the process of claim
 1. 7. Aflame-retardant cotton material made by the process of claim 1.